NEW YORK (Reuters Health)
— Doing yoga may help reduce blood pressure among people with
hypertension, a new analysis of past studies suggests.

“There is now a growing number of randomized
controlled trials on yoga for a variety of medical conditions,”
Holger Cramer told Reuters Health in an email.

But, he added, “the quality and expressiveness of these trials
varies, thus, it is often difficult to evaluate the real evidence
for the usefulness of yoga in a specific condition based on single
trials.”

Cramer led the review at the Faculty of Medicine at University of
Duisburg-Essen in Essen, Germany.

Previous studies have suggested yoga may be beneficial for a number
of health conditions, including irregular heart rhythms and
posttraumatic stress disorder (see Reuters Health stories of January
30, 2013 here: http://reut.rs/1jawFIW and April 18, 2014 here:
http://reut.rs/1hYvQY9).

“The current review on yoga for hypertension is part of this ongoing
project. In my opinion, since yoga is widely used all over the world
for a number of health issues, it is of crucial importance to
scientifically evaluate where it is useful - and where it is not,”
he said.

The findings were published in the American Journal of Hypertension.

Cramer and his colleagues combined the results of seven previous
studies that included 452 patients. In each of those studies, people
with high or borderline-high blood pressure were randomly assigned
to practice yoga for at least eight weeks or to get usual blood
pressure care or another type of treatment instead.

The researchers found that on average, yoga reduced systolic blood
pressure (the top number in a blood pressure reading) by about 10 mm
Hg and diastolic blood pressure (the bottom number) by 7 mm Hg,
compared to usual care.

When they looked only at patients with full-blown hypertension -
leaving out those with only slightly elevated blood pressure, or
“prehypertension” - the reduction in blood pressure was even
greater.

“We did, however, not find any effects in pre-hypertensive
patients,” Cramer said.

The National Institutes of Health defines high blood pressure as
140/90 mm Hg and above. Normal blood pressure is below 120/80 mm Hg,
and prehypertension is anything in the middle.

The review also found that yoga helped patients who were taking
blood pressure medication at the same time, but not those who used
it as an alternative to drugs.

However, the studies included in the review varied in ways that made
it difficult to evaluate the big picture of yoga’s effect on blood
pressure, the researchers said.

Two studies looked at specific yoga styles. One exclusively examined
the effect of yoga breathing techniques, and the rest involved some
combination of yoga postures and breathing techniques, relaxation,
meditation and lifestyle advice.

“While these findings are limited by the few available trials, we
found that yoga breathing seems to be more effective and safer in
persons with hypertension than more physically-oriented yoga forms,”
Cramer said.

The researchers also looked at the safety of yoga and found three
adverse reactions were reported in one of the studies. But it did
not specify what those involved.

Other studies have suggested that strains of the neck, shoulders,
legs and knees are common yoga injuries.

“An issue that is really important and generally underrepresented in
yoga research is the evaluation of the safety of the intervention -
in order to be able to precisely balance potential benefits and
potential harms for each individual patient,” Cramer said.

The lack of consistency between studies, and limitations in the
research methods they employed, means more research is needed, he
said.

“It is really important to have large, well-designed trials
available that fulfill the standards of today’s biomedical
research,” he said. “It might be worthwhile to conduct some more
trials that compare yoga to other forms of physical activity.”

Cramer recommends that people interested in yoga look for a style
that incorporates breathing techniques and relaxation with yoga
postures and look for a yoga teacher who has experience working with
people who try yoga for medical reasons.

“A licensed yoga therapist would be the best choice if available,”
he said.

Cramer added that patients should not stop taking their blood
pressure medication and should not to be too aggressive with their
yoga practice.

“Respect your limits; yoga is not about achievement and it should be
practiced mindful,” he said.